A typical table saw includes a base which supports a generally flat table top having a longitudinally extending slot and a pair of side rails extending along opposite sides of the table top generally perpendicular to the slot. The side rails are utilized for mounting a rip fence assembly to assist in positioning an article to be cut in relation to a cutting tool. A motor is mounted beneath the table top and the cutting tool, which may be a circular saw blade, is mounted for rotation with the powered output shaft of the motor. When the cutting tool is mounted directly to the shaft of the motor, or if the cutting tool is mounted to a transmission powered by the motor, the mounting of the motor and/or transmission is provided with adjustments which selectively position the cutting tool to extend through the slot in the table top. One adjustment for the motor and/or transmission determines the amount of the cutting tool which extends through the slot to control the depth of cutting. Another adjustment for the motor and/or transmission determines the angle of the cutting tool with respect to the table top to control the bevel angle or the angle of cutting. The cutting tool is thus positioned to project upwardly through the slot and is rotated by the motor with both the height of the cutting tool with respect to the table top and the angle of the cutting tool with respect to the table top being determined by the mounting mechanism for the motor and/or transmission. Cutting of the workpiece is normally accomplished by moving the workpiece longitudinally through the rotating cutting tool.
Machine tools are used for cross cutting (transverse cutting to the length of the workpiece), miter cutting (at an angle to the length of the workplace) and rip cutting (longitudinal cutting along the length of the workplace). For cross cutting and miter cutting, an angularly and laterally adjustable fixture or fence is used which positions the workplace perpendicular to or at the desired angle relative to the cutting tool. For rip cutting, a separate rip fence assembly is mounted on the side rails and positioned at a pre-selected distance from the cutting tool in order to perform the longitudinal or rip cutting operation on the workpiece.
When performing a cross cutting operation, a miter cutting operation or a rip cutting operation, it is advantageous to have the ability to control the depth of cut. This is accomplished by moving the saw blade generally perpendicular to the table top to change the amount of the cutting tool which extends through the table top. In addition, certain application will require the addition of a bevel angle during the particular cutting operation whether it be cross cutting, miter cutting or rip cutting. The introduction of a bevel angle is accomplished by angulating the cutting tool with respect to the table top or angulating the table top with respect to the cutting tool.
Manufacturers of power tool equipment have developed a variety of mechanisms which provide for both the height adjustment and the angular adjustment of the cutting tool with respect to the table top when the power tool is a direct drive power tool. The continued development of the height and angle adjustment mechanisms is directed towards systems which rigidly hold the cutting tool at the pre-selected position while maintaining a simple and easily actuated system for moving the cutting tool to other desired positions. The system should be as rigid as possible to provide accuracy during the cutting operation but should maintain an easily actuated mechanism to facilitate the changes required by the user. The system should provide the above advantages while keeping both the weight of the system and the costs to manufacture the system at a minimum.